The invention relates to a construction for preventing a scattering of a developing solution or cleaning liquid applied to the photosensitive member of an electrophotographic copying machine beyond the side or end face thereof.
Generally, an electrostatic latent image is formed in an electrophotographic copying machine by uniformly charging the surface of a photosensitive member having a photoconductive layer thereon, and selectively removing the surface charge by an image-imparting exposure. The latent image is converted into a visual image by applying to the surface on which it is formed a toner particle which is charged to the opposite polarity from that of the latent image. The developed image is brought into a superimposed relationship with a transfer sheet, to the rear side of which is applied a potential of sufficient magnitude and proper polarity, thus transferring the toner particle which forms the image onto the transfer sheet. The transferred image is fixed as by heating. On the other hand, there remains a certain amount of toner particle on the surface of the photosensitive member subsequent to the transfer step, and such particle is removed by a cleaning step. In the electrophotographic process mentioned above, liquid may be used in the developing station where a wet developing process is employed and also in the cleaning station where a liquid cleaning process is employed. Where such liquid is used, it is necessary to prevent the liquid from flowing to unintended portions to contaminate the apparatus or mar the image.
One of the proposals which have been made to prevent such an unintended liquid flow is illustrated in FIG. 1. In this FIG., a photosensitive member 1 is provided with a pair of developer troughs 2 outside the area in which an image may be formed, in order to prevent a flow of the developer toward the side or end face of the photosensitive member, thus preventing a marring of the image and contamination or failure of the machine. However, since the troughs are formed around the periphery of the photosensitive member 1 which rotates on a shaft 3, it will be seen that the troughs 2 also rotate, causing a scattering of the liquid contained in the troughs 2 under the influence of centrifugal force. Where a cleaning liquid is used, the liquid flow toward the side of the photosensitive member will be particularly increased at the position of the cleaning blade, so that a flange 4 which defines one side of the trough 2 must have an increased size. However, the presence of adjacent members makes it difficult to permit an increase in the size of the flange 4. As a consequence, this approach leaves much to be desired in preventing the liquid flow.
Another apparatus is shown in FIG. 2 in which a stationary member 14 having a groove 12 formed therein is located close to the respective opposite ends of a photosensitive member 11. While the photosensitive member 11 rotates on a shaft 13, the stationary members do not rotate, so that a scattering of the liquid contained in the groove 12 is avoided. However, there remains the second inconvenience mentioned above in connection with the apparatus shown in FIG. 1. Specifically, because the photosensitive member 11 rotates while the member 14 remains stationary, it is difficult to locate both of the members in exact conformity all around the periphery, particularly when the photosensitive member is in the form of a drum or an endless belt. Thus, a spillage or dripping of the liquid may result.